15-year-old TEDxVienna speaker Lalita Prasida worked with farmers in India to develop a wastewater filtration system using corn cobs (Photo: Lalita Prasida)

Fifteen-year-old Lalita Prasida was in school when she realized that — in many places around the world — potable water is a luxury. “[In my studies] I found that there’s a lot of impure water around, rather than pure water,” she says at TEDxVienna. “Potable water nowadays is very difficult to get.” Prasida wanted to change that, so she set out to create a new way to purify water.

Prasida, a resident of a rural village in remote India, started her mission after a conversation with a local farmer sparked her imagination. “In one of my encounters with a tribal farmer,” she writes in her description of her project, “I came to know about the low utilization of corn cobs, which ignited me to find out some ways to use this agricultural waste.” She had learned about how bioadsorbents (biological waste like fruit peels, eggshells, or shrimp shells) can be used to remove contaminants from water and she decided that corn cobs could be the perfect bioadsorbent for her village.

Farmers burned or dumped the inedible cobs, creating environmental pollution and waste that doesn’t biodegrade for a “long, long time,” Prasida says. She wondered if the cob, with its porous structure and durability, could be just as useful as the carbon or charcoal filters in your average water filtration pitcher.

She set out to find out. She designed a system that uses corn cobs four ways — as longitudinal sections, chunky pieces, powder and charcoal — (plus sand) to filter wastewater in steps.

Different forms of corn cobs for filtering water (Photo: Lalita Prasida)

After passing through these layers of bioadsorbents, Prasida found that polluted water became usable (though not potable). She hypothesized ways to set the system up in homes, so that residents could re-use graywater, and in businesses, so that industries would create less pollution.

She presented her findings at the Google Science Fair and won the Scientific American Community Impact Award for her work.

In the future, Prasida hopes her system could clean up ponds in her village and in others. “Ponds are the main source of fresh water for villagers,” Prasida says, “[but] fertilizer and pesticide runoff [go into] the pond water.” Prasida wants to create a system in which corn cobs are tied to bamboo poles and submerged in local ponds, so that pollutants will be trapped in the cobs’ pores.

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